Ducted air-cooled secondary of automobile battery charging transformer

Abstract: The inductive charge coupler (16) carrying the transformer primary is supplied with coolant fluid. The inductive charge receptacle mounted on the automobile (10) has interior cooling fluid passages and there is a duct to transfer the cooling fluid from the inductive charge coupler (16) to the cooling fluid passages in the inductive charge receptacle.

Description: The invention relates to a fluid-cooled transformer comprising an inductive charge coupler which includes a transformer primary comprising a primary transformer winding and magnetic permeable material; and an inductive charge receptacle defined by walls, to removably receive said inductive charge coupler, said inductive charge receptable including a transformer secondary which has a secondary transformer winding adjacent said inductive charge coupler when inserted in said inductive charge receptacle, and an associated magnetic permeable material. Such a transformer is known from EP-A-0 552 737. Generally, in charging the batteries of automobiles, a transformer primary inductive charge coupler is inserted into the transformer secondary inductive charge receptacle on the automobile, which charges the batteries of the automobile. The primary inductive charge coupler supplies ducted cooling air to cool the transformer secondary for increased performance. In order to reduce air pollution, there is a modern trend toward electrically powered automobiles. These electrically powered automobiles have rechargeable batteries therein. The power of the batteries is used to propel the automobile and to provide for other power needs thereof. The design of such a vehicle is a careful balance between payload, performance, range between charging, acceleration, and speed. No matter what the combination of these criteria, there is need to recharge the batteries periodically so that the automobile may be taken on another excursion. With fairly large batteries, there is need to recharge a substantial amount of power. Since the recharging time when an automobile is unavailable should be minimized, high charging rates are desirable. If an ordinary plug is to be used, the plug must be suited for high power, which brings about a risk of harm to the operator and/or other people in the vicinity from contact with parts of the electrical supply system. It is, thus, desirable to make a coupling between the charging station and the automobile which does not require the direct transfer of electricity. A magnetic coupling is desirable. In accordance with this invention, an inductive charge coupler can be manually handled and inserted in an appropriate inductive charge receptacle slot in the automobile. The inductive charge coupler is a transformer primary and contains an appropriate magnetic core. The inductive charge receptacle slot contains the transformer secondary winding(s) together with the rest of the magnetic core. The transformer secondary in the automobile is connected through appropriate electrical equipment to the battery for the charging thereof. The frequency is preferably higher than the ordinary power line frequency, and high charge rates are above 10 kilowatts. The result is that the amount of heat dissipated from the transformer coils, magnetic coils and other electronics contained within the inductively coupled separable transformer can exceed 50 watts. It is desirable to cool the entire transformer and its associated electronics, such as rectifiers, so that internal temperatures do not exceed the critical operating range of the materials used in the transformer, rectifier junction or surface touch temperatures to maximize performance. Cooling could be achieved by cooling devices in the automobile, but it is desirable to limit the total automobile weight as much as possible. It is, thus, desirable to improve the cooling methods for the inductive charge coupler. The above object is achieved by a transformer, mentioned at the outset, in that means are provided to supply coolant fluid to said inductive charge coupler, and further comprising walls defining a coolant fluid passage adjacent said transformer secondary, and a duct for ducting coolant fluid from said inductive charge coupler through said fluid passage adjacent said transformer secondary to said secondary winding. Generally, it is useful to employ offboard cooling sources to efficiently cool the transformer secondary coil and the related magnetic core. The use of offboard cooling at the charging station permits cooling air to be provided through the inductive charge coupler connections and inductive charge coupler. When the inductive charge coupler is inserted into the onboard transformer secondary inductive charge receptacle, there is direct coupling with internal air flow passages in the transformer secondary and associated electronics such as rectifiers and capacitors associated wit the inductive charge receptacle. This arrangement couples large offboard cooling capacity with onboard transformer and electronics cooling, thereby vastly extending the cooling capacity. As a result, the charging transformer can be more compact, lighter, more efficient and more reliable. This offboard cooling reduces the temperature of the entire transformer and associated electronics and reduces the surface temperature of the removable primary inductive charge coupler. In order to aid in the understanding of this invention, it can be stated in essentially summary form that it is directed to an inductive charge coupler which is connected to an offboard electric power supply and an offboard coolant supply, together with coolant fluid ducting in the inductive charge coupler and in the inductive charge receptacle at the transformer secondary on the car so that the transformer secondary is cooled. It is, thus, a purpose and advantage of this invention to provide a system for automobile battery charging which includes a transformer having a separable and cooled primary so that the primary may be energized from a stationary source and inserted into the transformer to energize the magnetic circuit therein and the electrical secondary circuit therein. It is another purpose and advantage of this invention to provide an automobile battery charging system which includes a transformer having a portion thereof separable from the automobile with the separable portion supplying cooling fluid from sources away from the automobile so that the separable portion delivers cooling fluid to the transformer secondary and other cooling needs on the automobile. It is another purpose and advantage of this invention to provide a transformer which is separable, with a portion mounted on a vehicle for the charging of the batteries on the vehicle and the other portion being separable and powered from an off-vehicle source. Cooling fluid is provided to the separable portion to cool the portion mounted on the vehicle to result in improved electrical performance and reduced temperature of the mounted portion. It is a further purpose and advantage of this invention to provide a separable automobile battery charging transformer, a portion of which remains on the automobile and a portion of which is separable therefrom so as to be permanently connected to a power supply. The separable portion delivers cooling fluid, which acts to cool the portion permanently installed in the automobile. Other purposes and advantages of this invention will become apparent from a study of the following portion of the specification, the claims and the attached drawings wherein: FIG. 1 is a perspective view of an electrically powered automobile which is connected to a stationary battery charging source. FIG. 2 is a section through the primary inductive charge coupler and secondary transformer inductive charge receptacle structure showing the cooling fluid path therethrough and through the associated electronics housing containing rectifiers. FIG. 3 is an exploded view of the structure shown in FIG. 2 to illustrate the fluid flow path. Automobile 10 is an automotive vehicle configured for the transportation of a few people and a small amount of baggage. It carries batteries which power motors which are connected to the road wheels. Suitable electrical and mechanical controls are provided to control the speed and direction of the vehicle. The onboard battery must be recharged periodically. In the system in accordance with this invention, charging power comes from a fixed power source 12 which is located adjacent the position where the automobile 10 will be parked when the owner is resting, working or shopping. In the present illustration, the automobile 10 is parked on its driveway 14 near the home of the owner of the automobile. It is presupposed by this invention that the automobile will not be directly powered from the power source 12 by means of a direct plug-in, but the charging connection will be inductive. A transformer is designed to receive power from the power source 12 and to deliver the power through magnetic coupling to a transformer secondary coil in the automobile. The secondary coil is appropriately connected through electronics to charge the automobile batteries. The power supply frequency is chosen in connection with the overall power supply parameters, including the transformer parameters. Inductive charge coupler 16, seen plugged into the automobile 10 in FIG. 1 and seen in enlarged sectional view in FIG. 2, is connected to the fixed power source by means of cable 18. The cable 18 incorporates the electrical connections. As seen in FIGS. 2 and 3, the inductive charge coupler 16 includes core 20, which is magnetically permeable such as ferrite and which is part of the magnetic circuit of the transformer. The balance of the magnetic circuit is in the automobile in association with the transformer secondary windings. Primary winding 22 surrounds the core 20 in a dielectric housing 24. Inductive charge coupler 16 includes a handle 26 by which the inductive charge coupler can be manually inserted into its inductive charge receptacle port in the automobile. The handle 26 receives the cable 18, as seen in FIG. 3. In addition to the electrical cable, the cable 18 includes a cooling fluid passage, preferably for cooling fluid which can be discharged to the atmosphere, such as air. The cooling fluid is pressurized and is preferably cooled below the ambient. Such can be conveniently achieved in the power source 12, which has neither power nor weight limitations. The fluid is delivered into the handle and into the fluid passage 28 in the inductive charge coupler, see FIG. 2. The cooling fluid may pass through passages in the inductive charge coupler which cool the core 20 and primary windings 22. In any event, at the end of its passage through the inductive charge coupler, it is discharged from inductive charge coupler outlets 30 and 32, see FIG. 2. The transformer secondary, which is magnetically coupled to the transformer primary in the inductive charge coupler includes cores 34 and 36 which face the core 20 and which are part of the magnetic circuit. The cores 34 and 36 are of magnetic material. In the inductive charge receptacle, secondary windings 38 and 40 surround the cores 34 and 36 and lie against the primary winding 22. Cooling plates 42 and 44 carry fins 46 and 48 thereon. The fins are open at the top and the bottom. Around the sides, the fins guide the coolant fluid directly adjacent the secondary. Receptable housing 50 surrounds the secondary windings and extends upward to the inductive charge receptacle port 52 in the automobile into which the inductive charge coupler is inserted. In that position, the secondary housing receives and controls the air exiting from the inductive charge coupler outlets 30 and 32. The only downward opening is adjacent the cooling plates 42 and 44 between the fins. At the bottom, the fins have an opening and the secondary housing has an opening so that the air is discharged out of the cooling fluid outlet 54. Electronics housing 56 is secured directly to the receptable housing 50 and receives the cooling fluid issuing from the cooling fluid outlet 54. Electronics housing 56 carries various electronics useful in the powering and control of the automobile 10. Of course, rectifiers are necessary to rectify the alternating current output of the secondary windings and regulate the voltage for the charging of the automobile batteries. Thus, rectifiers 58 and 60 are specifically shown in FIGURE 2. These rectifiers carry fins 62 and 64 in the coolant streams. Electronics 66 also carries fins in these coolant streams. The electronics 66 may be controlled electronics or may be additional rectifier structures. The exiting coolant streams 68 and 70 are exhausted from the system and preferably leaves the automobile. An exhaust fan may be applied to this stream, if necessary to provide the desired flow rate. In this way, offboard air which is properly routed with respect to the transformer secondary windings and magnetic field path during high-rate energy transfer provides higher cooling capacity because of the availability of higher coolant flow rates and refrigerated (if necessary) cooling air. In addition to the limiting of temperature in the transformer to keep the transformer component temperatures below critical values, it is also important to limit the temperature of the inductive charge coupler so that, when it is withdrawn at the end of a charging cycle, the inductive charge coupler surface temperature is sufficiently low as to not be harmful to the user. The outflowing coolant, preferably air, also cools the electronics. This invention has been described in it presently contemplated best mode, and it is clear that it is susceptible to numerous modifications, modes and embodiments within the ability of those skilled in the art and without the exercise of the inventive faculty. Accordingly, the scope of this invention is defined by the scope of the following claims.

Claims: A fluid-cooled transformer comprising: an inductive charge coupler (16) which includes a transformer primary (20, 22) comprising a primary transformer winding (22) and magnetic permeable material (20), an inductive charge receptacle defined by walls, to removably receive said inductive charge coupler (16), said inductive charge receptacle including a transformer secondary (34-40) which has a secondary transformer winding (38, 40) adjacent said inductive charge coupler (16) when inserted in said inductive charge receptacle, and an associated magnetic permeable material (34, 36), characterized by means to supply coolant fluid to said inductive charge coupler (16); walls (42-48) defining a coolant fluid passage adjacent said transformer secondary (34-40); and a duct for ducting coolant fluid from said inductive charge coupler (16) through said coolant fluid passage adjacent said transformer secondary (34-40) to said secondary transformer winding (38, 40). The fluid-cooled transformer of claim 1, characterized in that there are first and second secondary transformer windings (38, 40) and said walls (42-48) define first and second coolant fluid passages, respectively, adjacent said first and second secondary transformer windings (38, 40), and said first and second secondary transformer windings (38, 40) are on opposite sides of said inductive charge receptacle. The fluid-cooled transformer of claim 1 or claim 2, characterized in that a flexible cable (18) is connected to said inductive charge coupler (16) to supply electric power to said transformer primary (20, 22) and a flexible coolant fluid hose (18) is connected to said inductive charge coupler (16) to supply coolant fluid to said inductive charge coupler (16). The fluid-cooled transformer of any of claims 1 - 3, characterized in that said coolant fluid is a coolant gas. The fluid-cooled transformer of any of claims 1 - 4, characterized in that said inductive charge receptacle includes a receptacle housing (50) which surrounds said inductive charge coupler (16) where it enters said inductive charge receptacle, said housing (50) serving as a duct to duct coolant fluid from said inductive charge coupler (16) to said coolant fluid passages adjacent said transformer secondary (34-40). The fluid-cooled transformer of any of claims 1 - 5, characterized in that said secondary transformer winding (38, 40) is positioned in an automobile (10) and is connected to charge the battery in said automobile (10). The fluid-cooled transformer of any of claims 1 - 6, characterized in that a cable (18) is connected to an electric power source (12) and said inductive charge coupler (16) is connected to a source of coolant gas. The fluid-cooled transformer of claim 5, further characterized by an electronics housing (56) adjacent said receptacle housing (50) positioned so that said electronics housing (56) receives the coolant fluid issuing from said receptacle housing (50), electronics (58, 60, 66) in said electronics housing (56) positioned to be cooled by said coolant fluid so that coolant fluid issuing from said receptacle housing (50) passes through said electronics housing (56) to cool the electronics (58, 60, 66) therein. The fluid-cooled transformer of claim 8, characterized in that said electronics (58, 60, 66) comprises rectifiers (58, 60) connected to said transformer secondary (34-40). The fluid-cooled transformer of any of claims 1 to 9, characterized in that said magnetic permeable material (34, 36) of said transformer secondary (34-40) is a magnetic core (34, 36) associated with said secondary transformer winding (38, 40), said secondary transformer winding (38, 40) and its magnetic core (34, 36) included in said inductive charge receptacle (52), said walls (42-48) defining a cooling gas passage being positioned adjacent said secondary transformer winding (38, 40) ; said inductive charge coupler (16) has a flexible cable (18) connected thereto, and said transformer primary winding (22) is placed adjacent said secondary transformer winding (38, 40) so as to create magnetic coupling between said inductive charge coupler (16) and said secondary transformer winding (38, 40) for the transfer of electric power between said primary transformer winding (22) and said secondary transformer winding (38, 40); said supply means is a source of coolant gas connected to said inductive charge coupler (16), said inductive charge coupler (16) having a coolant gas outlet (30, 32) therefrom, said coolant gas outlet (30, 32) on said inductive charge coupler (16) being configured to deliver coolant gas to said coolant gas passage adjacent said transformer secondary to cool said secondary transformer winding (38, 40). The fluid-cooled transformer of claim 10, characterized in that a receptacle housing (50) engages said transformer secondary (34-40), said receptacle housing (50) also receiving said coolant gas from said coolant gas outlet (30, 32) on said inductive charge coupler (16) so that said receptacle housing (50) serves as a duct to duct coolant gas from said inductive charge coupler (16) to said coolant gas passage and adjacent said secondary transformer winding (38, 40). The fluid-cooled transformer of claim 10 or claim 11, characterized in that there are first and second secondary transformer windings (38, 40) and there is a slot between said secondary transformer windings (38, 40), said inductive charge coupler (16) is insertable into said slot, so that said primary transformer winding (22) magnetically couples to said secondary transformer windings (38, 40). The fluid-cooled transformer of any of claims 11 - 12, characterized in that said inductive charge coupler (16) is connected to a source (12) of electric power and said receptacle housing (50) is connected to a source of coolant gas. The fluid-cooled transformer of any of claims 10 - 13, characterized in that said walls defining a cooling gas passage adjacent said secondary transformer winding (38, 40) also define a cooling gas passage through an electronics housing (56), and further including electronics (58, 60, 66) in said electronics housing (56). The fluid-cooled transformer of claim 14, characterized in that said electronics (58, 60, 66) in said electronics housing (56) comprise rectifiers (58, 60) connected to said transformer secondary (34-40).

Inventors: HALL JOHN T, QOUN WILLIAM, TANZER HERBERT J, HALL, JOHN T., QOUN, WILLIAM, TANZER, HERBERT J.
Applicants: GEN MOTORS CORP, GENERAL MOTORS CORPORATION
Application year: 1994
Main classification: H01F38
IPC codes: H02J7, H02J17, H01F27, H01F38